‘67 Barracuda vacuum gauge connection
I hear ya! I bought some 'silicone' hose from Summit during that project. Problem is getting any real info about it.
Gates washer/vac hose is EPDM, which isn't bad.
At least in the Barracuda there's room to route stuff away from the heat. The 85 GWagoneer is a nightmare in that respect.
edit: Gates has some info on silicone hose, not OD, on the current website
Silicone vacuum tubing
Non-reinforced EPDM vacuum tubing
from the industrial engine hose catalog 2018. pdf